The Perils of DIY Headway LifePO4 Battery Building
Here are a few things to watch out for if you are building your own headway pack:
Charge All of the Cells . . .
A headway cells can read 3.2v and be nearly empty or quite full. So just becuase the volatges are "balenced" it does not mean that the charge levels are.
Use a single cell charger to charge all cells individually to 3.65v. This makes things a lot easier, becuase when you connect up yout BMS, it will not have to do so much balencing.
If you do not charge individually the BMS may takes WEEKS to balence the pack.
Watch that BMS! . . .
Do not trust your BMS, headway cells have a low internal resistance apprently so the BMS somthimes gets confused and will discharge your headway cells compleltly which kills them! So after rigging up your BMS, check to see that it is not discharging the cells.
Spending more on a BMS (ie. choosing qaulity) will not prevent this behaviour. Even a high qaulity BMS will do this. I do not understand why, just watch out for it.
Work in a Clear Area . . .You will need a screw driver / allen wrench / allen key to put your pack together, also perhaps some pliers etc. Keep these well away from the pack when not in use. If you place you pack on top of a metal object, it will short the terminals and you will get a big flash (which is scary) and also perhaps damage the cells.
Watch Order of Balencing Wires.. . .The order in which you connect the balencing wires from the controller will differ from BMS to BMS so make sure you get them in the write order. Read the instructions (if you are lucky enough to have any).
Always connect all of the balencing wires to the pack, before connecting the BMS.
Do not buy secondhand . . .This wholeprocess of headway DIY batteries is confusing enough without using secondhand cells. Some will be bad, and this will cuase problems. . . trust me you will have enough problems.
Conclusions . . . .Perhaps I am over confident but I have found building my own pack very difficult. I would recommend that you buy a preassessmbled pack, and learn by fixing it when it comes of age. Componenets are expensive and you do not need to damage many befor ethe costs equal that of a pre-built pack.
Save youself the hassle and buy a ready made battery pack.